1. Field of the Invention
The present invention relates to a short-range wireless communication apparatus which performs information communication with, e.g., a so-called contactless IC card reader/writer and to a cellular phone terminal having the short-range wireless communication apparatus.
2. Description of the Related Art
In recent years, a contactless IC card (hereinafter referred to as an RFID card) having a built-in RFID (Radio Frequency-Identification) circuit has been coming into wide use as, e.g. a train ticket and a prepaid card because the RFID card has the advantages of good usability, excellent durability, simultaneous accessibility to multiple cards, easy maintenance, etc.
Further, since a cellular phone terminal having the RFID card built-in has been commercialized recently, by electronically transferring monetary information between the RFID card incorporated into the cellular phone terminal and a contactless IC card reader/writer (hereinafter referred to as an RFID card reader/writer) provided at e.g. a store, it is possible to pay for a purchase at the store etc.
Hereinafter, a description will be made on the flow of communication operation in an RFID system composed of an RFID card incorporated into a mobile terminal such as a cellular phone terminal and an RFID card reader/writer provided at a store etc. As a specific example of the RFID system, the flow of communication operation in the so-called Felica (trademark) system is described below.
First, in the RFID system, the RFID card reader/writer (not shown) always transmits carrier waves and polling commands.
In the case where the cellular phone terminal having the built-in RFID card is close to the RFID card reader/writer, the RFID card incorporated into the cellular phone terminal activates by receiving a carrier wave transmitted from the RFID card reader/writer. Upon receiving a polling command transmitted from the RFID card reader/writer, the RFID card determines whether the received polling command conforms to a service installed in the RFID card. Only if the received polling command conforms to the service, the RFID card sends a response to the RFID card reader/writer.
Next, when the RFID card sends a response to the RFID card reader/writer as described above, mutual authentication is performed between the RFID card reader/writer and the RFID card. Afterward, the RFID card reader/writer reads and writes data in the RFID card as necessary.
When the series of processes is completed correctly, the RFID card reader/writer notifies a user that the series of processes has been completed correctly in a specified manner of the RFID system. Specified manners in which the RFID card reader/writer notifies a user that the series of processes has been correctly completed include manners such as sounding a specified alarm from a speaker connected to the RFID card reader/writer and displaying a specified indication on the screen of the display connected to the RFID card reader/writer.
FIG. 4 is a schematic circuit diagram of a transponder section of the RFID card.
In FIG. 4, a loop antenna 101 receives a carrier wave having a frequency of 13.56 MHz transmitted from the RFID card reader/writer (not shown) and generates the potential difference of a waveform corresponding to the magnetic field change of the carrier wave between antenna terminals 101a and 101b. The antenna terminals 101a and 101b is connected to the RFID function LSI (Large Scale Integration) 110.
Further, a tuning capacitor 102 exists between the antenna terminals 101a and 101b and the RFID function LSI 110. The tuning capacitor 102 is a capacitor for producing a resonance frequency of 13.56 MHz, combined with an inductance component of the loop antenna 101.
Furthermore, a rectifier diode 103 exists between the antenna terminal 101b and the RFID function LSI 110. The rectifier diode 103 shifts a voltage waveform on the loop antenna 101 to a plus side relative to the ground (GND), thereby allowing the RFID function LSI 110 operated by a single power source to easily process the voltage waveform. The rectifier diode 103 is also used for extracting a direct-current (DC) power source from the carrier wave received by the loop antenna 101.
The RFID function LSI 110 includes a receiving circuit 112 for performing demodulation to extract a 212-kHz signal component out of the so-called ASK (Amplitude Shift Keying) modulated carrier wave from the RFID card reader/writer, a transmitting circuit 113 for modulating a transmission signal, an FET (Field Effect Transistor) circuit 114 for switching a load, an MPU (Micro Processing Unit) 115 for implementing a clock extraction circuit and a higher layer of a wireless communication protocol, and a non-volatile memory (not shown). Further, the resistor 104 for adjusting a load modulation rate is connected to the RFID function LSI 110.
Further, a lock signal for disabling or enabling the RFID card function is provided to an enable input terminal of the RFID function LSI 110 via a lock signal input terminal 105. The lock signal is low at the time of disabling the RFID card function.
Further, Japanese Patent Application Laid-Open No. 2004-266729 (patent document 1) discloses the following technique. In a cellular phone terminal having a contactless IC card built-in, when the contactless IC card is close to a reader/writer so that an induced voltage in the contactless IC card caused by a carrier wave from the reader/writer exceeds a predetermined voltage, a CPU (Central Processing Unit) in the cellular phone terminal lights an LED (Light Emitting Diode) in yellow for example, thereby notifying a user that the contactless IC card has come so close to the reader/writer that they can communicate with each other. Next, when the contact less IC card receives a start command from the reader/writer, the CPU in the cellular phone terminal lights the LED in blue for example, thereby notifying the user that communication processing between the contactless IC card and the reader/writer has started. Moreover, when data communication is being performed between the contactless IC card and the reader/writer, the CPU in the cellular phone terminal blinks the LED in blue for example, thereby notifying the user that data communication is being performed between the contactless IC card and the reader/writer.
[Patent document 1] Japanese Patent Application Laid-Open No. 2004-266729 (FIG. 1)